Transwitch Corporation

Kumar Shakti Singh

Pawan Goyal

Daniel C Upp

Ashis Maitra

Pushkal Yadav

Sachin Mathur

Diljit Singh

Chitra Wadhwa

Yudhishthira Kundu

Edward Soltysiak

Vikas Kumar

Arnab Basak

Amandeep Singh Gujral

Time multiplexed processing of multiple SONET signals uses the same shared circuitry for framing, descrambling, maintenance signal processing, control byte processing and extraction, pointer tracking, retiming, and alarm indication. The signals are deserialized and multiplexed onto a byte-wide bus from which they are processed in a shared pipeline. Additional pipelines allow scaling up to higher capacity SONET signals. Each pipeline is provided with means for communicating with the other pipelines so that information derived from the processing of one stream can be shared with the processing of other streams when necessary. According to the presently preferred embodiment, bytes pass through the pipeline in five clock cycles.

Time multiplexed SONET line processing

The excessive bit error rate detection algorithm operates in two modes: BURST mode and non-BURST mode. In non-BURST mode, an alarm state is entered if an error count exceeds a threshold within a set number of frames and exits the alarm state when the error count stays below a threshold for a set number of frames. In the BURST mode, the alarm state is not entered unless the error count exceeds the threshold two consecutive times and does not exit the alarm state unless the error rate remains below a threshold for two consecutive frame counts.

Methods and apparatus for burst tolerant excessive bit error rate alarm detection and clearing

Methods for retiming and realigning SONET signals include demultiplexing STS-1 signals from an STS-3 signal, buffering each of the three signals in a FIFO, determining the FIFO depth over time, determining a pointer leak rate based in part on FIFO depth and also based on the rate of received pointer movements. For a 28-byte deep FIFO, if the depth of a FIFO is 12-16 bytes, no pointer leaking is performed. If the depth is 0-4 bytes, an immediate positive leak is performed. If the depth is 24-28, an immediate negative leak is performed. If the depth is 5-11 bytes a calculated positive leak is performed. If the depth is 17-23 bytes, a calculated negative leak is performed. The calculated leak rates are based on the net number of pointer movements (magnitude of positive and negative movements summed) received every 32 seconds (256,000 frames).

Methods and apparatus for retiming and realigning sonet signals

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Kumar Shakti Singh